Many industrial applications involve components (i.e., wear-parts) which are subjected to wear during the life time of the part. The use of parts that requires wear-resistance are quite common in cement, mining and thermal power generation industries. When a wear-part is worn down, the part must be replaced. Consequently, any device using the wear-part cannot be used as the part is being replaced; the replacement of a worn out wear-part leads to a loss in operative time of the device. Therefore, an improvement in the wear resistance of a wear-part component would lead to a decrease in percentage of time lost due to replacing such worn components and increase the effectiveness of the wear-part.
Historically, 12% Mn steel and Ni-hards were used for wear resistant wear-parts applications during first half of twentieth century. During the last 50 years, high chromium irons have been successfully used for wear resistant wear-parts applications and have largely replaced Ni-hard and 12% Mn steel based materials.
The search for further improved wear resistance in wear-parts has continued, and in the past last 15 years, ceramic cakes and in particular metal matrix ceramic composites (MMCC) have been used with varying degree of success for wear resistant wear-parts applications. FIG. 1 illustrates a ceramic cake of the prior art. The ceramic cake 1 comprises ceramic grains 2 and often a binder 3. The binder in FIG. 1 is schematically represented as a thin layer around some of the grains. FIG. 2 illustrates a ceramic cake of the prior art infiltrated with metal. To impregnate the ceramic cake, molten metal is introduced. The molten metal fills the spaces between the grains 2 to form a matrix for the ceramic grains to produce a “metal matrix ceramic composite” part (MMCC). The ceramic material in MMCC's are usually in the form of grains, with alumina being a typical choice as it is known to be a good abrasive material.
In this regard, U.S. Pat. No. 3,181,939 (issued May 4, 1965; assigned to Norton Company, Mass, USA) to Douglas W. Marshal describes the manufacture of fused alumina zirconia abrasives which combine good wear resistance characteristics of alumina and the toughness of zirconia. Thus, alumina/zirconia grains appear to be a suitable candidate for metal matrix ceramic composites. Ullmann's Encyclopedia of Industrial Chemistry, Fifth Complete revision, part A1, Volume A1, paragraph 2.2 describes useful alumina/zirconia grains.
The art of preparing wear resistant parts by casting with embedded hard material is described in a German patent (by Dr. Wahl) No. 7326661; issued Jul. 20, 1973.
Japanese Patent No. 62286661 to Mr. Tamura of KiH (issued, Dec. 12, 1987) describes a method of impregnating ceramic particles with molten metal to produce composite casting with good wear resistance.
European Patent No. EP 0575858B1 filed by Staub Fritz (issued Jun. 23, 1992, assignee Zuzel Inotech AG) describes production of metal matrix ceramic composite casting with porous ceramic members at the wearing face. The ceramic particles used are described as corundum, zirconium oxide or magnesium oxide.
U.S. Pat. No. 6,399,176 (issued Jun. 4, 2002) describes the production of composite wear components by casting in which ceramic cakes were introduced on the wear surface, the ceramic cakes consisting of homogeneous solid solution of 20-80% alumina and 80-20% zirconia.
Although there are many examples of composite wear-parts, there remains a need in the art for further improvements to the property of wear resistance to these wear-parts.